Get Tech Tips
Subscribe to get free tech tips.
A REALLY Loud Compressor
A while ago, I walked up on one of our managers who was talking to a junior tech diagnosing an intermittent controls issue on a pool heat pump.
In the background, you could hear an EXTREMELY loud compressor.
The junior tech had just been moving some wires around, and the next thing he knew, there was a clack and then the noisy compressor and equalized pressures.
Do you know what happened yet?
I instructed him to shut it off and asked if it was a scroll compressor.
Sure enough, it was.
What happened was an instantaneous short cycle caused by the loose connector being moved. In that split second, the high-pressure gas in the scroll forced the scroll plate in the opposite direction ever so slightly. Once the power came right back on, it was running backward.
Now, this really shouldn't happen, but when it does happen, it's because of one of a few reasons.
Three-phase miswiring
When a new three-phase building is constructed or a new unit or compressor is installed, it is possible to miswire the phases, resulting in a compressor running backward. This is not a good thing, but it can be corrected by switching any two legs of incoming power.
Instantaneous short cycling
This is what happened in the case of my junior tech. In most cases, the time delay in a board, thermostat, or controller will prevent this from occurring. Sometimes, the cause is internal to the system due to loose connections, etc.
Miswiring or Failed Capacitors
In single-phase applications, the run capacitor applies a phase-shifted potential that helps get the motor running and keeps it running. If the capacitor has failed or the compressor is miswired, it can occasionally (rarely) result in it running backward.
Failed Discharge Check Valve
Most scroll compressors have either an internal or external check valve that prevents the discharge gas from forcing back through the compressor, causing it to spin backward.
Occasionally, you may find a scroll compressor that makes a loud whirring once it cycles off. That can usually be corrected by installing a discharge check valve or by replacing the compressor if you choose.
Finally, be aware that anytime a scroll runs backward, it can do significant damage. If you find one that's running backward, shut it off immediately and correct the cause.
—Bryan
Related Tech Tips
Comments
What is the picture at top?
What is the picture at top?
ProDentim 4zz duplicate. ProDentim breath fresh all day. Finally.
ProDentim 4zz duplicate. ProDentim breath fresh all day. Finally.
Marketing Blocks AI. Marketing Blocks AI created my entire sales funnel in 1 hour. Game changer.
Marketing Blocks AI. Marketing Blocks AI created my entire sales funnel in 1 hour. Game changer.
Rocket Languages 4zz duplicate. Rocket Languages spoke fluently on trip. Best course.
Rocket Languages 4zz duplicate. Rocket Languages spoke fluently on trip. Best course.
GlucoBerry 4zz duplicate. GlucoBerry doctor impressed. Natural.
GlucoBerry 4zz duplicate. GlucoBerry doctor impressed. Natural.
Hyperbolic Stretching. Hyperbolic Stretching back pain gone. Life changing.
Hyperbolic Stretching. Hyperbolic Stretching back pain gone. Life changing.
Yes, another relationship guide. Make Him Worship You focuses on emotional triggers. My guy became more attentive.
Yes, another relationship guide. Make Him Worship You focuses on emotional triggers. My guy became more attentive.
Sell what you know. Course Creator System made $5k in 30 days. Step by step blueprint.
Sell what you know. Course Creator System made $5k in 30 days. Step by step blueprint.
Love. His Secret Obsession made him plan a surprise getaway. Finally.
Love. His Secret Obsession made him plan a surprise getaway. Finally.
Dog training. Kingdom of Pets plays nicely now. Finally peace.
Dog training. Kingdom of Pets plays nicely now. Finally peace.
Long term prep. The Lost Superfoods and hardtack. Essential knowledge.
Long term prep. The Lost Superfoods and hardtack. Essential knowledge.
Practice. Meditation Mastery calm in 2 minutes. Life skill.
Practice. Meditation Mastery calm in 2 minutes. Life skill.
Still my go-to focus tool. The Brain Song helps me get through boring reports faster. 7 minutes a day is plenty.
Still my go-to focus tool. The Brain Song helps me get through boring reports faster. 7 minutes a day is plenty.
Affilorama 1b4u. Affilorama open rate doubled. Old school but gold.
Affilorama 1b4u. Affilorama open rate doubled. Old school but gold.
But you can fight back. MetaboFlex targets the root hormone issue. No jitters, just steady energy.
But you can fight back. MetaboFlex targets the root hormone issue. No jitters, just steady energy.
I almost gave up my feline. Cat Spraying No More fixed it in 4 days. House smells normal again.
I almost gave up my feline. Cat Spraying No More fixed it in 4 days. House smells normal again.
Weight. Mitolyn energy up. Natural.
Weight. Mitolyn energy up. Natural.
Weight. CitrusBurn feeling great. No plateau.
Weight. CitrusBurn feeling great. No plateau.
Exipure 4zz duplicate. Exipure lost 14 lbs in 8 weeks. Natural.
Exipure 4zz duplicate. Exipure lost 14 lbs in 8 weeks. Natural.
Passive. Perpetual Income 365 quit my job. Freedom.
Passive. Perpetual Income 365 quit my job. Freedom.
Energy Liberation Army duplicate. Energy Liberation Army abundance flowing. Deep work.
Energy Liberation Army duplicate. Energy Liberation Army abundance flowing. Deep work.
Weight loss side effect. LivPure lost 10 lbs and energy doubled. Natural support.
Weight loss side effect. LivPure lost 10 lbs and energy doubled. Natural support.
Deepen. Meditation Mastery taught me to meditate anywhere. Essential skill.
Deepen. Meditation Mastery taught me to meditate anywhere. Essential skill.
Wealth frequency audio. Billionaire Brain Wave got an unexpected $200. Coincidence? Maybe not.
Wealth frequency audio. Billionaire Brain Wave got an unexpected $200. Coincidence? Maybe not.
Wealth frequency still humming. Billionaire Brain Wave boss just offered it. I’m convinced.
Wealth frequency still humming. Billionaire Brain Wave boss just offered it. I’m convinced.
Dog training. Kingdom of Pets manners improved. Finally.
Dog training. Kingdom of Pets manners improved. Finally.
Ted’s Woodworking 4zz duplicate. Ted’s Woodworking perfect plans. Saved $200.
Ted’s Woodworking 4zz duplicate. Ted’s Woodworking perfect plans. Saved $200.
What I love about this one is how quickly it works. I use it every morning now.
What I love about this one is how quickly it works. I use it every morning now.
I was self-conscious about my breath until Fresh Breathies killed bad breath instantly. I keep a bottle in my car and purse.
I was self-conscious about my breath until Fresh Breathies killed bad breath instantly. I keep a bottle in my car and purse.
What I love about The Brain Song is how quickly it works. I use it every morning now.
What I love about The Brain Song is how quickly it works. I use it every morning now.
I’ve used a lot of brainwave tracks, but this one within 10 minutes I’m in the zone. I use it every morning now.
I’ve used a lot of brainwave tracks, but this one within 10 minutes I’m in the zone. I use it every morning now.
Affilorama Affilorama Affilorama -> Affilorama made my first $100.
Affilorama Affilorama Affilorama -> Affilorama made my first $100.
Enjoy a premium airport transfer Dubai experience with luxury vehicles like Rolls Royce or Bentley. Choose private airport transfer Dubai for a seamless ride from the airport to your hotel, ensuring comfort and style throughout your journey.
Enjoy a premium airport transfer Dubai experience with luxury vehicles like Rolls Royce or Bentley. Choose private airport transfer Dubai for a seamless ride from the airport to your hotel, ensuring comfort and style throughout your journey.
This is the info iv’e been looking for!! Thanks!!
This is the info iv’e been looking for!! Thanks!!
My first experience with a scroll compressor with a failed check valve was 1993 when a client called me and said his unit makes a horrible noise when it turns off. I went out and while the heat pump was running, I pulled the disconnect. When I did this, the compressor started spinning backwards and was also generating 288 volts to the outdoor fan motor, which was really spinning fast. As the pressures equalized, the voltage kept dropping until the compressor stopped altogether. Yes, when refrigerant spins the compressor, it becomes a generator. Really messed with me for a little until I found out that Rheem had snuck this compressor into this unit as an experimental test. The compressor was in an insulated box so you could not see that it was different. This model had always had a recip in it before. Rheem provided a new compressor. Brian.
My first experience with a scroll compressor with a failed check valve was 1993 when a client called me and said his unit makes a horrible noise when it turns off. I went out and while the heat pump was running, I pulled the disconnect. When I did this, the compressor started spinning backwards and was also generating 288 volts to the outdoor fan motor, which was really spinning fast. As the pressures equalized, the voltage kept dropping until the compressor stopped altogether. Yes, when refrigerant spins the compressor, it becomes a generator. Really messed with me for a little until I found out that Rheem had snuck this compressor into this unit as an experimental test. The compressor was in an insulated box so you could not see that it was different. This model had always had a recip in it before. Rheem provided a new compressor. Brian.
It appears that installing external check valves on scroll compressors (as a backup) would be a good idea.
It appears that installing external check valves on scroll compressors (as a backup) would be a good idea.
I wonder why the engineers overlooked that? Reciprocating compressors have discharge valves inherent in their designs that positively keep the refrigerant from flowing back into the compress. (Providing they aren’t leaking of course)
I wonder why the engineers overlooked that? Reciprocating compressors have discharge valves inherent in their designs that positively keep the refrigerant from flowing back into the compress. (Providing they aren’t leaking of course)
A start kit has remedied this issue for me so far. I have seen this a few times and found it hard to believe that a single phase would do this. Was close to changing out the compressor on a so called “lemon” (customers opinion) when the thought came to me about a start kit possibly getting the jump on the correct rotation. This unit has a moderately long (65′) line-set that I thought might have a migration issue. After crankcase heaters had been applied the issue would still occasionally happen.
A start kit has remedied this issue for me so far. I have seen this a few times and found it hard to believe that a single phase would do this. Was close to changing out the compressor on a so called “lemon” (customers opinion) when the thought came to me about a start kit possibly getting the jump on the correct rotation. This unit has a moderately long (65′) line-set that I thought might have a migration issue. After crankcase heaters had been applied the issue would still occasionally happen.
To leave a comment, you need to log in.
Log In